Reconfigurable Phase Change Device

ABSTRACT

A reconfigurable phase change device with methods for operating and forming the same are disclosed. An example device can comprise a reconfigurable layer comprising a phase change material, and a set of contacts connected with the reconfigurable layer. The set of contacts can comprise at least a first contact, a second contact, and a third contact. The device can comprise at least one control element electrically coupled with one or more of the set of contacts. The at least one control element can be configured to supply a first control signal to one or more of the set of contacts. The first control signal can be configured to modify a first portion of the reconfigurable layer thereby isolating the first contact from the second contact and the third contact.

CROSS REFERENCE TO RELATED PATENT APPLICATION

This application claims priority to U.S. Provisional Application No.61/983,132 filed Apr. 23, 2014, and U.S. Provisional Application No.61/983,129 filed Apr. 23, 2014, herein incorporated by reference intheir entirety.

BACKGROUND

Reconfigurable logic devices, such as reconfigurable arrays, are mainlytransistor based, wherein multiple transistors are utilized to switchbetween the inputs and outputs. Reconfigurable arrays can also be madeby utilizing antifuses or other types of nonvolatile memory (NVM)elements. However, scalability, configuration time, access speed, andcomplexity of fabrication process for current reconfigurable logicdevices needs to be improved to reach their full potential in devices ofcommercial value. These and other shortcomings are addressed by thedisclosed devices and processes.

SUMMARY

It is to be understood that both the following general description andthe following detailed description are exemplary and explanatory onlyand are not restrictive, as claimed. The present disclosure relates to areconfigurable device, methods of operating the device, and afabrication process thereof. An example device (e.g., apparatus) cancomprise a reconfigurable layer comprising a phase change material and aset of contacts connected to the reconfigurable layer. The set ofcontacts can comprise at least a first contact, a second contact, and athird contact. The example device can comprise at least one controlelement electrically coupled to one or more of the set of contacts. Theat least one control element can be configured to supply a first controlsignal to one or more of the set of contacts. The first control signalcan be configured to modify a first portion of the reconfigurable layerthereby isolating the first contact from the second contact and thethird contact.

In another aspect, an example method can comprise forming a first statein a reconfigurable layer by applying a first control signal to one ormore of a set of contacts electrically connected to the reconfigurablelayer. The set of contacts can comprise at least a first contact, asecond contact, and a third contact. The first control signal can modifya first portion of the reconfigurable layer thereby isolating the firstcontact from the second contact and the third contact. A first dataoutput can be received from the reconfigurable layer based on the firststate of the reconfigurable layer. The reconfigurable layer can beswitched to a second state by applying a second control signal to one ormore of the set of contacts electrically connected to the reconfigurablelayer. The second control signal can change which of the set of contactsare isolated or not isolated. A second data output can be received fromthe reconfigurable layer based on the second state.

In another aspect, an example method can comprise melting a firstportion of a phase change structure between a first contact connected tothe phase change structure and a second contact connected to the phasechange structure. An amorphous region can be formed around the firstportion. The first portion can be crystallized thereby forming aconductive path from the first contact to the second contact. Theconductive path can be isolated, by the amorphous region, from a thirdcontact connected to the phase change structure. A first signal can beprovided through the conductive path.

In another aspect, an example method can comprise forming a first set ofelectrodes on a substrate. A first insulating layer can be depositedupon the substrate and first set of electrodes. A well can be formed inthe first insulation layer. A reconfigurable layer can be formed bydepositing a phase change material upon sidewalls the well. The firstset of electrodes can be electrically connected to a bottom of thereconfigurable layer. A second set of electrodes electrically connectedto a top of the reconfigurable layer can be formed.

In another aspect, an example apparatus can comprise a medium and a setof contacts connected to the medium. The set of contacts can beconfigured to cause at least a first path in the medium and a secondpath in the medium. The apparatus can comprise a control elementelectrically coupled to the set of contacts and configured toselectively couple a source to the set of contacts. A first coupling ofthe source to the set of contacts can cause the first path to becomemore conductive than the second path. A second coupling of the source tothe set of contacts can cause the first path to become more conductivethan the second path.

In another aspect, an example method can comprise coupling a source to aset of contacts configured to channel the source across a medium thougha first path and a second path. Coupling the source can cause the firstpath to become more conductive than the second path. The source can beuncoupled from the set of contacts. Uncoupling the set of contacts cancause the first path to become less conductive than the second path. Thesource can be recoupled to the set of contacts. Recoupling the set ofcontacts can cause the second path to become more conductive than thesecond path.

In another aspect, an example method can comprise providing a firstcommand signal to a device to cause a first state in the device. Thedevice can comprise a set of contacts configured to channel commandsignals through one or more of a first path and a second path. Theportion of the first command signal can be channeled through the firstpath thereby cause the second path to become more conductive. A firstoutput signal can be received from the device based on the first state.A second command signal can be provided to the device to cause a secondstate in the device after receiving the first output signal. At least aportion of the second command signal can be channeled through the secondpath thereby causing the first path to become more conductive. A secondoutput signal can be received based on the second state.

Additional advantages will be set forth in part in the description whichfollows or may be learned by practice. The advantages will be realizedand attained by means of the elements and combinations particularlypointed out in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate embodiments and together with thedescription, serve to explain the principles of the methods and systems:

FIG. 1A illustrates the conductivity profile for a reset operationshowing an amorphized volume as a result of utilizing a slow rise pulse;

FIG. 1B illustrates the conductivity profile for the reset operationshowing the amorphized volume as a result of utilizing fast rise pulseresulting in filament formation across the top and bottom contacts;

FIG. 2A illustrates a simulated 8-contact reconfigurable device with2-inputs, 2-outputs, and 4-write terminals in a first state;

FIG. 2B illustrates the simulated 8-contact reconfigurable device with2-inputs, 2-outputs, and 4-write terminals in a second state;

FIG. 3 is a three-dimensional schematic view of a wrapped phase changedevice;

FIG. 4 is a three-dimensional schematic view of a phase change pipe;

FIG. 5 illustrates an exemplary process for forming a reconfigurabledevice;

FIG. 6A shows a model of a conductivity profile of the reconfigurabledevice after sending two write words;

FIG. 6B shows a peak thermal profile for applying write pulses to thereconfigurable device;

FIG. 7 is a table illustrating some configurations of a reconfigurabledevice along with the corresponding write commands and truth tables;

FIG. 8A is an illustration of connection formed by two contacts using avoltage pulse;

FIG. 8B is an illustration of voltage pulses used over time to configurethe reconfigurable device as shown in FIG. 8A;

FIG. 9 illustrates a thermal profile for a PCM cell simulated using 2Drotational symmetry showing the filament formation;

FIG. 10 illustrates a two-in put two-output phase-change deviceimplementing 5 distinct functions;

FIG. 11A illustrates an 8-contact reconfigurable device in a firststate;

FIG. 11B illustrates an 8-contact reconfigurable device in a secondstate;

FIG. 11C illustrates an 8-contact reconfigurable device in a thirdstate;

FIG. 12A illustrates a 2-input one output toggle multiplexer using asingle control input;

FIG. 12B illustrates input and output signals for an examplemultiplexer;

FIG. 13 illustrates a reconfigurable device having 7 contacts;

FIG. 14 illustrates a resistivity map showing connectivity after severaltoggle operations;

FIG. 15 illustrates conductivity maps for stages of an electro-thermalsimulation for a toggle operation;

FIG. 16A is a block diagram illustrating an example reconfigurabledevice;

FIG. 16B is a block diagram illustrating the example reconfigurabledevice after reconfiguration;

FIG. 17 is a flow chart illustrating an example method for operating areconfigurable device;

FIG. 18 is a flow chart illustrating another example method foroperating a reconfigurable device;

FIG. 19 is a flow chart illustrating another exemplary method foroperating a reconfigurable device;

FIG. 20 is a flowchart illustrating another exemplary method foroperating a reconfigurable device;

FIG. 21A is a schematic showing an example reconfigurable device;

FIG. 21B illustrates the relationship between an input signal (A) andthe output signal (Y);

FIG. 21C illustrates an alternative configuration of the reconfigurabledevice;

FIG. 22A illustrates an example reconfigurable device configured as adeterministic device variant;

FIG. 22B shows the relationship between the input signal A and theoutput signal Y;

FIG. 23 illustrates the size comparison of a typical toggle multiplexerto a reconfigurable device configured as a toggle multiplexer;

FIG. 24 illustrates another example reconfigurable device;

FIG. 25 illustrates another example reconfigurable device;

FIG. 26A illustrates an initial state (all crystalline) of thereconfigurable device;

FIG. 26B illustrates sending one pulse to transistor B;

FIG. 26C illustrates sending another pulse to transistor B;

FIG. 26D illustrates sending another pulse to transistor C;

FIG. 26E illustrates sending a pulse to transistor A;

FIG. 26F illustrates sending another pulse to transistor A;

FIG. 26G illustrates sending another pulse to the transistor A;

FIG. 27 illustrates an example reconfigurable device;

FIG. 28 illustrates a schematic of an example reconfigurable device;

FIG. 29 illustrates another schematic of an example reconfigurabledevice;

FIG. 30 illustrates another schematic of an example reconfigurabledevice;

FIG. 31A illustrates another schematic of an example reconfigurabledevice;

FIG. 31B is a graph illustrating the relationship of resistance andtemperature of the device of FIG. 31A;

FIG. 32A illustrates another schematic of an example reconfigurabledevice;

FIG. 32B is a graph illustrating the relationship of resistance andtemperature of the device of FIG. 32A;

FIG. 33A illustrates another schematic of an example reconfigurabledevice;

FIG. 33B is a graph illustrating the relationship of resistance andtemperature of the device of FIG. 33A;

FIG. 34A illustrates another schematic of an example reconfigurabledevice;

FIG. 34B is a graph illustrating the relationship of resistance andtemperature of the device of FIG. 34A;

FIG. 35A illustrates another schematic of an example reconfigurabledevice;

FIG. 35B is a graph illustrating the relationship of resistance andtemperature of the device of FIG. 35A;

FIG. 36 is a flowchart illustrating an example method for operating areconfigurable device; and

FIG. 37 is a flowchart illustrating an example method for operating areconfigurable device.

DETAILED DESCRIPTION

Before the present methods and systems are disclosed and described, itis to be understood that the methods and systems are not limited tospecific methods, specific components, or to particular implementations.It is also to be understood that the terminology used herein is for thepurpose of describing particular embodiments only and is not intended tobe limiting.

As used in the specification and the appended claims, the singular forms“a,” “an,” and “the” include plural referents unless the context clearlydictates otherwise. Ranges can be expressed herein as from “about” oneparticular value, and/or to “about” another particular value. When sucha range is expressed, another embodiment includes from the oneparticular value and/or to the other particular value. Similarly, whenvalues are expressed as approximations, by use of the antecedent“about,” it will be understood that the particular value forms anotherembodiment. It will be further understood that the endpoints of each ofthe ranges are significant both in relation to the other endpoint, andindependently of the other endpoint.

“Optional” or “optionally” can mean that the subsequently describedevent or circumstance may or may not occur, and that the descriptionincludes instances where said event or circumstance occurs and instanceswhere it does not.

Throughout the description and claims of this specification, the word“comprise” and variations of the word, such as “comprising” and“comprises,” means “including but not limited to,” and is not intendedto exclude, for example, other components, integers or steps.“Exemplary” can mean “an example of” and is not intended to convey anindication of a preferred or ideal embodiment. “Such as” is not used ina restrictive sense, but for explanatory purposes.

Disclosed are components that can be used to perform the disclosedmethods and systems. These and other components are disclosed herein,and it is understood that when combinations, subsets, interactions,groups, etc. of these components are disclosed that while specificreference of each various individual and collective combinations andpermutation of these may not be explicitly disclosed, each isspecifically contemplated and described herein, for all methods andsystems. This applies to all aspects of this application including, butnot limited to, steps in disclosed methods. Thus, if there are a varietyof additional steps that can be performed it is understood that each ofthese additional steps can be performed with any specific embodiment orcombination of embodiments of the disclosed methods.

The present methods and systems can be understood more readily byreference to the following detailed description of preferred embodimentsand the examples included therein and to the Figures and their previousand following description.

As will be appreciated by one skilled in the art, the methods andsystems can take the form of an entirely hardware embodiment, anentirely software embodiment, or an embodiment combining software andhardware aspects. Furthermore, the methods and systems can take the formof a computer program product on a computer-readable storage mediumhaving computer-readable program instructions (e.g., computer software)embodied in the storage medium. More particularly, the present methodsand systems can take the form of web-implemented computer software. Anysuitable computer-readable storage medium can be utilized including harddisks, CD-ROMs, optical storage devices, flash memory internal orremovable, or magnetic storage devices.

Embodiments of the methods and systems are described below withreference to block diagrams and flowchart illustrations of methods,systems, apparatuses and computer program products. It will beunderstood that each block of the block diagrams and flowchartillustrations, and combinations of blocks in the block diagrams andflowchart illustrations, respectively, can be implemented by computerprogram instructions. These computer program instructions can be loadedonto a general purpose computer, special purpose computer, or otherprogrammable data processing apparatus to produce a machine, such thatthe instructions which execute on the computer or other programmabledata processing apparatus create a means for implementing the functionsspecified in the flowchart block or blocks.

These computer program instructions can also be stored in acomputer-readable memory that can direct a computer or otherprogrammable data processing apparatus to function in a particularmanner, such that the instructions stored in the computer-readablememory produce an article of manufacture including computer-readableinstructions for implementing the function specified in the flowchartblock or blocks. The computer program instructions can also be loadedonto a computer or other programmable data processing apparatus to causea series of operational steps to be performed on the computer or otherprogrammable apparatus to produce a computer-implemented process suchthat the instructions that execute on the computer or other programmableapparatus provide steps for implementing the functions specified in theflowchart block or blocks.

Accordingly, blocks of the block diagrams and flowchart illustrationssupport combinations of means for performing the specified functions,combinations of steps for performing the specified functions and programinstruction means for performing the specified functions. It will alsobe understood that each block of the block diagrams and flowchartillustrations, and the combinations of blocks in the block diagrams andflowchart illustrations, can be implemented by special purposehardware-based computer systems that perform the specified functions orsteps, or combinations of special purpose hardware and computerinstructions.

The present disclosure relates to reconfigurable devices, such as aphase change devices, along with associated methods for operating andforming the same. In an aspect, non-conducting (e.g., amorphized) pathscan be formed electrically in a reconfigurable device by high-voltage,short-duration pulses (e.g., a reset operation) in a crystalline oramorphous medium, and the non-conducting (e.g., amorphized) paths can beused to isolate a first set of contacts (e.g., input contacts) and asecond set of contacts (e.g., output contacts), thus implementing adesired functionality. In an aspect, conducting paths can be madebetween a first set and a second set of contacts by applyinglong-duration (e.g., in the order of 10s of nanoseconds) low-voltage(e.g., in the order of 0.1 V) pulses between the first set and secondset of contacts, when the phase change material (PCM) is amorphous. Inan aspect, the crystalline-to-amorphous phase transition can be utilizedto form highly resistive paths that isolate different device contacts(e.g., terminals, electrodes), forcing the current to flow throughinsulated crystalline paths. In an aspect, different amorphized pathscan result in a different device configuration in terms of addressingcertain inputs to certain outputs. Thus, the reconfigurable device canbe used in reconfigurable logic applications as well as signal routingapplications.

In an aspect, a disclosed method for fabricating the disclosedreconfigurable device can comprise forming a first set of contacts on asubstrate, depositing a first insulation layer on the substrate and thefirst set of contacts, forming a well in the first insulation layer andthe first set of contacts, depositing a layer of phase change material(PCM) on the first insulation layer. The layer of PCM can comprise ahole that aligns with the well. The method can further comprisedepositing a second insulation layer on the layer of phase changematerial, and forming a second set of contacts on the second insulationlayer. The reconfigurable device can also be achieved using differentphase change materials, such as GST, GeTe, SbTe, and combinationsthereof. The reconfigurable device can be embodied in variousconfigurations with differing number of contacts, arrangements, anddimensions.

In an aspect, the disclosed reconfigurable device can be a single deviceconfigured to route signals without the need of external wiring. In anaspect, the reconfiguration time for the reconfigurable device can befast (e.g., in the order of 100 ns). In an aspect, the disclosed devicecan be a strong candidate for the in-processor logic operations and canbe used to replace the conventional switching mechanisms and signalrouting in the low-power reconfigurable electronics applications. Forexample, the reconfigurable device can be used for a phase-changememory. In an aspect, the fabrication process for the disclosed devicecan be simple. The fabrication process of the reconfigurable device canenhance the scalability of the device, as the dimensions of thereconfigurable device can be in the order of nanometers.

FIG. 1A and FIG. 1B illustrate various aspects of an exemplaryenvironment in which the present methods and systems can operate.Specifically, FIG. 1A and FIG. 1B show a conductivity profile for areset operation. FIG. 1A shows the amorphized volume as a result ofutilizing a slow rise time pulse FIG. 1B shows the amorphized volume asa result of utilizing a fast rise time pulse. Utilizing a fast rise timepulse can result in filament formation across the top and bottomcontacts. In an aspect, Ge₂Sb₂Te₅ (GST) chalcogenide alloy can be usedas a phase change material. The resistivity of GST can be a function oftemperature. Specifically, the amorphous and crystalline-FCCresistivities can decay exponentially with a temperature increaseresulting in thermal runaway. In PCM mushroom cells, for example,utilizing reset pulses with a fast rise time pulse and providingsufficient current can lead to formation of elongated filaments acrossthe device terminals due to thermal runaway as shown in FIG. 1B.

FIG. 2A and FIG. 2B illustrates an example reconfigurable device. Thedevice can comprise a phase change device. The reconfigurable device cancomprise an 8-contact phase-change device. For example, thereconfigurable device can comprise 2-inputs (e.g., I₁, I₂). The devicecan comprise 2-outputs (e.g., O₁, O₂). The reconfigurable device cancomprise 4-write terminals (e.g., W₁, W₂, W₃, W₄). The reconfigurabledevice can be integrated with digital (binary) CMOS which can have railto rail operation, namely, inputs and outputs are either high (1) or low(0) access FETs for inputs. The outputs can be scalable depending on thefan-out configuration and is not limited by write current requirements.In an aspect, filament formation can be utilized to melt, amorphize,and/or the like different paths in a multi-contact geometry. Forexample, the simulated device shown in FIG. 2A and FIG. 2B can beimplemented on a rectangular thin film GST patch making contact with twoinput (e.g., I₁,I₂) and two control (e.g., W₁,W₂) terminals on one side,two output (e.g., O₁,O₂), and two control terminals (e.g., W₃,W₄) onanother side as shown in FIG. 2A and FIG. 2B. In an aspect, theimplementation can be performed by control terminals, and can be read bythe input and output terminals. Passing enough current with fast risetime pulses through control terminals can form an amorphized path,resulting in a configuration that can alter the connection between theinputs terminals and outputs terminals. For example, activatingtransistors W₁, W₃ at the same time (i.e., sending the write command(e.g., W₁=1, W₂=0, W₃=1, W₄=1, wherein 1 represents a 2 V pulse) canamorphize the path between them. Consequently, a path betweentransistors W₂ and W₄ can be amorphized by sending the write word (e.g.,W₁=0, W₂=1 W₃=0 W₄=1). The write word can result in a specificconfiguration where I₂ can be connected to O₁ and I₁ can be connected toO₂ by crystalline paths that can insulated from each other by the highlyresistive amorphized paths. Other configurations of the GST patch can beachieved by sending different writing commands as shown in FIG. 2B.

The functionality of the disclosed phase change device can depend on howphase change material elements are integrated with CMOS. In an aspect,if I/O terminals can be used for the write operation, rise times,voltages (or currents), and coordination of the I/O waveforms can becontrolled and read using smaller voltages. Alternatively, the disclosedreconfigurable devices can be configured to have dedicated write andread terminals, as shown in FIG. 2A and FIG. 2B, making an eightterminal structure for 2-bit operation. This approach can reducecomplexity associated with the write and read operations and can beeasier to integrate with digital (binary) CMOS which has rail to railoperation (inputs and outputs are either high (1) or low (0)). In a 2Dpatch, all I/O connectivity combinations other than swap function(Output 1=Input 2, Output 2=Input 1) can be achieved.

FIG. 3 is a 3D schematic view of a illustrating an examplereconfigurable layer 300. The reconfigurable layer 300 can beimplemented as a flat (e.g., substantial two-dimensional) planar layer.In some scenarios, the reconfigurable layer 300 can be formed asthree-dimensional shape, such as a tube or pipe shape. Suchconfiguration can be visualized as planar layer that is wrapped to forma tube shape. This can be illustrated, for example, as connecting twosides (i.e., left and right edges) of a planar reconfigurable layer asshown in FIG. 3. Such three-dimensional shape can allow a reconfigurabledevice to implement a swap function. For example, the swap function canbe implemented because input terminals coupled to the reconfigurablelayer can be connected to either one of the output terminals coupled tothe reconfigurable layer.

FIG. 4 is a schematic view of an example reconfigurable device 400. Inan aspect, the reconfigurable device can comprise a reconfigurable layer402. The reconfigurable layer 402 can comprise a phase change material,such as GST. The reconfigurable layer 402 can be formed as tube, a pipe,and/or or other shape. For example, the height and the diameter of thereconfigurable layer 402 can be significantly larger (e.g., three timesand more) than the wall thickness of the reconfigurable layer 402, asshown in FIG. 4. The reconfigurable device 400 can comprise inputcontacts 404. The input contacts 404 can be connected to a first side406 of the reconfigurable layer, such as a top or bottom of thereconfigurable layer 402. The reconfigurable device 400 can compriseoutput contacts 408. The output contacts 408 can be connected to asecond side 410 of the reconfigurable layer 402, such as a top or abottom of the reconfigurable layer 402. The first side 406 can beopposite from the second side 410. The reconfigurable device 400 canalso comprise one or more control contacts 412 and 414. For example thecontrol contacts can comprise a first set 412 of control contacts. Thefirst set 412 of control contacts can be located on the first side 406.The one or more control contacts can comprise a second set 414 ofcontrol contacts. The second set 414 of control contacts can be locatedon the second side 410. In an aspect, the reconfigurable layer 402 canbe disposed around an insulating layer 416 comprising, silicon dioxideor other suitable material.

FIG. 5 illustrated an exemplary fabrication procedure. In an aspect, anexample reconfigurable device can be fabricated using a side-wallprocess. Step (a) illustrates forming a thermal oxide layer on a Sisubstrate. Step (b) illustrates depositing of a first metal layer. Step(c) shows etching the metal layer to form a first set of electrodes(e.g., a cross with 4 contacts). Step (d) illustrates depositing a SiO₂layer. Step (e) shows forming a well using a lithography technique andan etching technique of the SiO₂ layer. Step (f) shows etching the firstmetal layer. Step (g) illustrates depositing GST, using reactive ionetching (RIE). Step (h) illustrates forming a GST side-wall. Step (i)illustrates depositing a second insulating layer (SiO₂ or Si₃N₄). Step(j) illustrates planarization. Step (k) illustrates depositing a secondmetal layer. Step (j) illustrates forming a second set of electrodes. Itshould be noted that the same structure can also be achieved using acubic geometry. For example, a cube can be formed. Then, a well (e.g.,cylindrical, cubic shaped) can be formed in the cube. For example, anyhollow structure having a closed surface (e.g., along at least oneaccess) with open ends can be utilized.

As an example, a fabrication process for the reconfigurable device cancomprise forming a first set of contacts on a substrate, depositing afirst insulation layer on the substrate and the first set of contacts,forming a well in the first insulation layer and the first set ofcontacts, depositing a layer of phase change material (PCM) on the firstinsulation layer, wherein the layer of PCM can comprise a hole thataligns with the well, depositing a second insulation layer on the layerof phase change material, and forming a second set of contacts on thesecond insulation layer.

A film made of phase change material (e.g., GST) can be deposited on avariety of materials such as SiO₂, Si₃N₄, and topographies and annealedfor densification using infrared, microwave and furnace annealing. Thefilm can be characterized in physical term and electrical term. In anaspect, the disclosed phase change device can be fabricated using thefilm with desired characteristics. In an aspect, computational tools canbe used to evaluate necessary conditions for the device operations,functional implementation and the necessary access devices. Thedisclosed device can be integrated with circuits and architectures forcomputation using computational tools. FIG. 6A and FIG. 6B illustrate anexemplary modeled reconfigurable device with dimensions in nm.Specifically, the reconfigurable device can be modeled by aL×W×D=120×100×20 nm GST layer with eight TiN contacts. Periodic boundaryconditions can be applied at the left and the right sides of the layerso that both the left side and the right side act as if they areconnected to each other to imitate a tube structure. In an aspect, thereconfigurable device 600 can be a sandwiched structure between twolayers of SiO₂ of 100 nm of thickness. FIG. 6B shows a peak thermalprofile for applying a 2 V write pulse that activates transistors W₁ andW₄ (e.g., with write commands W₁=1, W₂=0, W₃=0, W₄=0). White contourlines denote the boundaries of melting in an active region. FIG. 6Ashows a model of a conductivity profile of the reconfigurable device 600after sending two write words (e.g., 1001; 0101). The amorphized regionsof the reconfigurable layer are shown in a lighter shade whilecrystallized regions are shown in a darker shade.

In an aspect, FIG. 6A and FIG. 6B illustrate an example reconfigurabledevice 600 in which terminal spacing is staggered. If the top writecontacts (W₁, W₂) are aligned with the bottom write contacts W₃, W₄, theterminal spacing can be non-uniform to achieve deterministic writeoperations. For example, if the spacing between the set of contacts isequal, the current will have two equally probable paths to flow in. Thisconfiguration can lead to nondeterministic operation of the device. Oneway of causing the operation to be deterministic is by having differentspacing between the contacts (non-uniform spacing). In such case, thecurrent will always have a more preferable path to follow. Otherwise,clock-wise and counter-clock wise current paths may be equally likely.An alternative approach, shown in in FIG. 6A and FIG. 6B, can be tostagger top write terminals and bottom write terminals (e.g., W₁ alignedwith O₁, I₁ aligned with W₃, etc.). This staggered configuration canforce current flow in diagonal paths. The amorphized filaments formed bythe current can form diagonals and can be deterministic, which canalleviate complexity associated with a set operation (e.g., center partof amorphized filaments do not need to be recrystallized).

In an aspect, the reconfigurable device 600 can be implemented inhigh-performance logic for non-volatile routing, multiplexing,functional implementation and data storage for significantly lower poweroperation as the endurance problems are alleviated.

FIG. 7 is a table illustrating possible configurations of amorphized andconductive paths. The table shows write commands used to form thecorresponding configurations. The table shows the resulting input/outputfunctionality (e.g., illustrated as a truth table) that can beimplemented via the corresponding configurations of the reconfigurabledevice.

In an aspect, an example reconfigurable device can be configured toconnect any pair of contacts (e.g., input terminals and outputterminals). The reconfigurable device can also isolate the connectionfrom the rest of the contacts (e.g., input terminals and outputterminals). In an aspect, characteristic nucleation-growth dynamicsapproach can be used to form a nano-scale conducting path that issurrounded by an insulating amorphous region. For example, the amorphousregion can heat up by the application of an electric filed. A nucleationprocess (e.g., creation of a crystalline portion) will start based on aprobability of nucleation that relates to the raised temperature (e.g.,higher probability in a certain temp range depending on the materialused). The number of the formed nuclei can depend on the duration duringwhich the amorphous region is heated to the high probability nucleationtemp range. If the temperature is raised further to a growth temperaturerange, a growth process can become dominant and the formed nuclei canstart growing to form a conductive path between contacts through whichthe electric filed is applied. The contacts (e.g., input terminals andoutput terminals) can be used for control signals and data signals. Inan aspect, higher voltage control signals and/or synchronization can beused to form of conductive paths.

FIG. 8A and FIG. 8B illustrate an example process for forming aconductive path between two contacts of an example reconfigurabledevice. For example, the reconfigurable device can be configured to forma conductive path between a first contact and a second contact. First, avoltage pulse can be applied between the first contact and the secondcontact as shown in FIG. 8B. The voltage pulse can melt a wide pathbetween the first contact and the second contact. Connection of twocontacts in a crystalline GST block with a liquid filament can be turnedinto a coaxial structure of crystalline GST path enclosed in anamorphous insulation layer. In a 3D geometry, a large number ofconnections can be formed from a top contact array to the bottom contactarray, limited by the density of the contacts. In an aspect, a newfilament can avoid amorphized enclosure of the other filaments. In anaspect, thermal losses and heating profile can play an important role information of the connections. In an aspect, reconfigurable routing insmall volumes can makes it difficult to reverse-engineer circuitstructures using cross-sections and transmission electron microscopy(TEM) analysis, which can be useful for security applications.

In an aspect, the voltage applied between the first contact and thesecond contact can be reduced thereby leaving only the central part ofthe molten region as liquid (filament-retention) as shown in step (a).The portion of the melted region surrounding the liquid region can beamorphous, as shown in step (b).

In an aspect, the inner part of the amorphized region can start tocrystallize via nucleation and growth as shown in step (c). The currentapplied between the first contact and the second contact can begradually reduced to crystallize a core region via growth-from-melttemplate from the adjacent crystalline shell, as shown in step (d). Theresulting core region can be a conductive path formed between the firstcontact and second contact. The conductive path can be surrounded withan insulating amorphous layer (shell).

Accordingly, the reconfigurable device can be used in resistive (i.e.,non-volatile) memory technologies. The resistive memories can utilizereversible changes in resistance of a small volume of material. Thisresistance change can be achieved by magneto-resistance such as inmagnetic RAM (MRAM) or by utilizing electro-thermal effects. In anaspect, large resistance contrast can be achieved by employing phasechange material, giving rise to metal-insulator transition, as inphase-change memory (e.g., PCM or PCRAM).

In an aspect, the reconfigurable device can be used for computation. Thereconfigurable device can be used for logic functions used incomputation. For example, the reconfigurable device can be integratedinto a computing circuit, such as a general purpose CPU, fieldprogrammable gate array (FPGA), application specific integrated circuits(ASICS), and/or the like. For example, a typical CPU may cost more andconsume more power than a FPGA or ASIC, but the CPU may offer the mostflexibility. Power consumption can be significantly lowered byintegration of the reconfigurable device with such computing device.Such integration may reducing leakage and enable efficient hibernationwithout accessing off-chip memory.

In another aspect, the reconfigurable device can be used as a componentof switches as well as components in neural networks. For example, thereconfigurable device can be configured to implement functions andreconfigurable routing. In another aspect, the reconfigurable device canbe implemented with a CMOS configuration. This hybrid phase-change andCMOS approach can have the potential to utilize non-volatility of phasechange elements of the reconfigurable device and inherit amplificationof CMOS for low-power computation. In an aspect, the reconfigurabledevice can utilize materials and concepts used for phase change memoryelements in alternative geometries (e.g., tube) that enable functionalimplementation. The reconfigurable device can be integrated with CMOSelements to map functions and/or enable reconfigurable routing ofsignals. As such, the endurance of PCM elements can be significantlyimproved, enabling use of the reconfigurable device for efficient andnon-volatile programming of logic operations.

FIG. 9 illustrates the formation of a conductive filament in an examplereconfigurable device. Thermal profiles are shown over time (e.g.,starting in time at the top left and ending at the bottom right). Thethermal profiles of the reconfigurable device are simulated using 2Drotational symmetry. The thermal profiles illustrate thermal runaway andfilament formation during reset with a rise time (e.g., 0.5 ns). In thisscenario, the rise time is not enough for heat to diffuse sufficientlywithin the phase change material. As the heat diffuses, the filament canretract (e.g., shrink). The volume experiencing melting (e.g., whitecontours) can be amorphized upon resolidification. Though thereconfigurable device is not limited to such configuration, the bottomcontact can have a diameter of 12 nm and the reconfigurable layer can bebiased through a field effect transistor (FET).

FIG. 10 illustrates an example reconfigurable device. The reconfigurabledevice can comprise a two-input two-output phase-change deviceimplementing 5 distinct functions illustrated as a first function (f₁),a second function (f₂), a third function (f₃), a fourth function (f₄),and a fifth function (f₅). The first function can provide a signal tooutputs O₁ and O₂ based on a signal supplied to input I₁. The secondfunction can provide a signal to outputs O₁ and O₂ based on a signalsupplied to input I₂. The third function can provide the input I₁ to theoutput O₁ and the input I₂ to the output O₂. The fourth function canprovide no output from output O₂ while providing signals from I₁ and I₁to output O₁. The fifth function can provide no output from Output O₁while providing signals from I₁ and I₁ to output O₁.

In aspect, the reconfigurable device can be configured to perform one ormore of these functions based on formation of amorphous regions aroundor otherwise proximate to one or more of the contacts. For example,amorphous regions can be formed to isolate different contacts toconfigure the reconfigurable device for functions f₁, f₂, f₄, and f₅.For function f₁, input I₂ is isolated from the other input and outputs.For function f₂, input I₁ is isolated from the other input and outputs.For function f₄, output O₂ is isolated from the other input and outputs.For function f₅, output O₁ is isolated from the other input and outputs.

In an aspect, the reconfigurable device can be configured to performthese functions based on filament formation. For example, filamentformation between various contacts can be utilized to melt and amorphizedifferent paths in a multi-contact geometry, enabling multi-inputmulti-output device configurations. For example, function f₃ can beimplemented by forming a filament, path, line and/or the like betweenoutput contact O₁ and input contact I₂. By way of explanation, thereconfigurable device can comprise a reconfigurable layer, such as asubstantially two-dimensional thin film. If the thickness of thereconfigurable layer is much smaller than the other two dimensions ofthe reconfigurable layer, two or more sections of the plane can beisolated from each other using amorphized lines in the reconfigurablelayer of the reconfigurable device.

In an aspect, output of function f₄ and f₅ can depend on access devicesand terminal configurations. For example, if the reconfigurable deviceis read by passing current then a different functionality is achievedbased on the inputs states.

A thermal runaway and a conductive filament can be formed if thereconfigurable device is operated above a threshold speed. Functions canbe written by controlling the voltage levels, rise-times and durations.For example, the time constants associated with heat diffusion can be 10⁻⁹ to 10 ⁻⁸ seconds.

FIG. 11A, FIG. 11B, and FIG. 11C illustrate an 8-contact phase-changedevice with 2-inputs, 2-outputs and 4-write terminals. In an aspect, arectangular reconfigurable layer (e.g., a GST patch) can be in contactor otherwise be electrically coupled with two input terminals on a firstside of the reconfigurable layer and two output terminals on a secondside of the reconfigurable layer. The geometry can allow for isolationof one or both of the input terminals or the output terminals, and thus,functionalization. In an aspect, the input terminals can be used forwrite operations. The rise times and voltage (or current) can becontrolled for the reset operation. A read can be achieved using a lowervoltage (e.g., in the order of 100 mV). The device can give all thefunctionality of a two-input, two output configuration other than theswap function (e.g., swap: Output₁=Input₂, Output₂=Input₁), implementing5 unique configurations. Access FETs for inputs and outputs can bescalable depending on the fan-out configuration, and not limited byreset current requirements. Hence the block with access FETs can besmaller than 8 PCM cells with access FETs. Functions can be written byturning on pairs of write terminals. Three sample functions are shownwhere the amorphized path (dark color) is used to isolate terminals.

In an aspect, input/output devices can be fabricated to implementcombinations of three or more inputs and outputs. The implementation candepend on how CMOS is integrated with the input of the devices. Forexample, input signals can be connected to the gate of one or moreaccess transistors or directly into the reconfigurable device resultingin slightly different write operation and truth table. Alternatively,the devices can be configured to have dedicated write terminals and readterminals as shown in FIG. 11A, FIG. 11B, and FIG. 11C. Writeoperations, which reconfigure the reconfigurable layer, can be performedby the dedicated terminals. Read operations can be performed by theinput and output terminals.

In an aspect, an example reconfigurable device can comprise fourdedicated write terminals (e.g., with two input terminals and two outputterminals). The reconfigurable device can thus, comprise an 8 terminalstructure configured for a 2-bit operation. Such configuration (e.g.,having dedicated write terminals) can reduce the complexity associatedwith the write and read operations and allow for easier integration withdigital (binary) CMOS, which has rail to rail operation (inputs andoutputs are either high (1) or low (0)). The dimension restrictions on aplurality of input transistors and output transistors can be alleviated,and fan-in and fan-out can be implemented relatively easily. Superiorfunctionality can be achieved by using the write terminals, which enableimplementation of a swap function in which each of input terminals canbe connected to either one of the output terminals.

In an aspect, the reconfigurable device can be configured to change itsconfiguration through a consistent clock/control signal. For example,the reconfigurable device can work as a 2×1 non-volatile signalmultiplexer, such as a T-Flip-flop, which is a fundamental buildingblock of digital electronic system used in computers and communicationsystems. In an aspect, the reconfigurable device can comprise areconfigurable layer. The reconfigurable layer can comprise asubstantially two-dimensional thin film in a rectangular shape (e.g.,assuming the thickness of the film is much smaller compared with theother two dimensions).

As an example, the reconfigurable device can be built such that aplurality of (e.g., six) contacts (e.g., metal contacts) can beinterfaced with a plurality of (e.g., five) transistors. The plurality(e.g., six) of contacts can comprise control terminals (e.g., two),input terminals (e.g., two) and/or output terminals (e.g., two).

In an aspect, the reconfigurable device can comprise a plurality oftransistors. For example, the control terminals can be connected to asingle transistor (e.g., NMOS), while the two input terminals and thetwo output terminals can be connected to four corresponding transistors(e.g., PMOS). In an aspect, PMOS and NMOS can be interchanged.

When a first control signal is sent, a potential difference can beformed between two control terminals across the reconfigurable layer andtwo equally probable paths of currents can be formed. Due to materialnon-uniform nature and process variations, one of the two paths can takeover and short circuit the other path, leading to asymmetric meltingbetween the two control terminals. A highly resistive amorphous path canbe then formed during rapidly cooling of molten volume. The amorphouspath can isolate one input terminal from the output terminals. The otherinput terminal can remain connected to the output terminals by thecrystalline phase change material. When a second control signal is sent,a current can flow between intact control terminals as it has a moreconductive current path. For example, the first control signal and thesecond control signal can be the same. This signal can be applied to thesame set of contacts. However, each time the signal is provided, thesignal can adjusts, modify, reconfigure, and/or otherwise change thedevice to a different state. For example, the reconfigurable device cantoggle between two states (e.g., because of the thermal crosstalk). Thepreviously amorphized path can then crystallize if the second controlsignal is maintained for sufficient time (e.g., because of thermalcrosstalk). Accordingly, the other input terminal can be connected tothe output terminals. This process can be repeated every time a controlpulse is sent, leading to toggling the input terminals. In an aspect,simulation results show successive cycles with consistent behavior. Thepulse durations and fall-times can be designed along with the geometryto achieve desired performance. It should be noted that, although thesimulation results are shown for certain transistor types, thereconfigurable device can be operable with a different phase changematerial and transistor configuration. For example, a different numberof contacts, arrangements, and dimensions can be used in thereconfigurable device. In an aspect, the reconfigurable device cancomprise different phase change materials, such as Ge₂Sb₂Te₅ (GST),GeSb, GeTe, SbTe and other chalcogenides.

In an aspect, the reconfigurable device can be used to implement logicin general purpose CPUs, field programmable gate arrays (FPGAs) orapplication specific integrated circuits (ASICS). The reconfigurabledevice can reduce power requirements for such devices. Along with thereduction in power, performance can be significantly boosted byincreased capacity for parallel computations. For example, use of thereconfigurable device can allow for a large-density of non-volatileelements to be integrated with a CPU, FPGA, ASIC, and/or the like.

In an aspect, phase-change elements can be used as switches as well aspart of neural network. Multi-contact phase change elements can permitimplementation of functions and reconfigurable routing, going beyond PCMuse for look-up tables. In an aspect, complementing CMOS withphase-change elements can offer significant advantages over conventionalCMOS in circuit footprint (area) and standby power. In an aspect, thedisclosed multi-contact phase-change device can perform multiplexing anddata routing.

In an aspect, an example reconfigurable device can be configured asmultiplexer. For example, the reconfigurable device can be configured toswitch between different outputs. In an aspect, the reconfigurabledevice can comprise a reconfigurable layer, such as a 2D-planarphase-change patch. The reconfigurable device can be implemented with atleast two slightly different geometries (e.g., 6 contacts or 7contacts). The reconfigurable layer can be interfaced with 5 CMOStransistors (toggle-multiplexer) capable of achieving 2-input, 1-outputmultiplexing using 1-control terminal with a total of 6 or 7 contacts asshown in FIG. 12A and FIG. 13. For example, FIG. 12A and FIG. 12Billustrate a 2-input (e.g., X₁, X₂), one output (e.g., Y) togglemultiplexer using a single control input (A). As another example, FIG.13 illustrates a reconfigurable device with a 7 contact arrangement witha narrow GST patch.

FIG. 14 illustrates a resistivity map showing connectivity after severaltoggle operations. In an aspect, the reconfigurable device can beconfigured to switch between two different amorphized paths. In someconfigurations, the reconfigurable device can be configured to amorphizeonly one path at a time. As an illustration, the reconfigurable devicecan amorphize a first path within the reconfigurable layer. Then, thereconfigurable device can amorphize a second path within thereconfigurable layer. During amorphization of the second path, the firstpath recrystallizes. The output can toggle from one input to the otherwith incoming control pulses.

In an aspect, the reconfigurable device can be configured as aT-flip-flop. For example, with fixed 0, 1 inputs, the reconfigurabledevice can act as a T-flip-flop. The T-flip-flop implemented by thereconfigurable device can have approximately 50% less footprint comparedto a conventional CMOS T-flip-flop with an additional advantage ofnon-volatility (allowing intermittent use/power).

In an aspect, in a geometry shown in FIG. 12A, an example reconfigurabledevice can comprise nFETs to control the control (e.g., write)terminals. The reconfigurable layer can comprise pFETs to control thedata (e.g., read) terminals. It should be noted, that a read operationcan be disabled during reconfiguration of the reconfigurable layer. Insome scenarios, gates of the FETs can share the same control signal (A).When a control pulse is received in A, a more conductive path canself-heat and melt. During this process, the amorphized regions (darkercolor) can recrystallize as shown in FIG. 14. As the pulse isterminated, a molten region can be amorphized, hence in ahigh-resistance state, a toggle operation can be achieved.

FIG. 15 illustrates frames of a conductivity map from an electro-thermalsimulation for a toggle operation of the reconfigurable device. Lightercolors are more conductive. The gray contour lines highlight theboundary of the molten regions. As shown in steps (i)-(iv), thereconfigurable device can be initialized in a crystalline state and amolten filament can be formed between C₂ and C₃, leaving an amorphizedregion at the end of the pulse, as shown in step (v), setting themultiplexer to Y=X₁ state. A second pulse (e.g., identical to the first)can form a molten path between C₁ and C₃ and crystallize previouslyamorphized areas, as shown in steps (vi)-(vii). With termination of thepulse, a multiplexer can be set to Y=X₂ state and one cycle of toggleoperation can be achieved, as shown in step (viii). In an aspect, cyclescan continue in the same fashion, as shown in step (ix). Simulationresults show successive cycles with consistent behavior. Pulse durationsand fall-times can be designed along with geometry to achieve desiredperformance.

In an aspect, a reconfigurable device with bottom metal contacts can befabricated. The bottom metal contacts can be fabricated using trenchformation (e.g., photo-lithography and reactive ion etching (RIE)),metal deposition and chemical mechanical polishing (CMP). As an example,GST thin films can be deposited using atomic layer deposition (ALD) andget capped with SiO₂ (ALD).

In an aspect, the disclosed reconfigurable device can be integrated withSilicon based CMOS. In an aspect, silicon based CMOS devices can befabricated for the control circuitry to test accurate evaluation ofcircuit performances. The redesign can include improvements based onexperiences in the earlier phases. CMOS flow may require additionallithography steps.

In an aspect, the reconfigurable device can be formed as follows. Aphase change material, such as GST, can be deposited using atomic layerdeposition (ALD). Atomic layer deposition (ALD) is a conformal thin filmdeposition technique which can provide atomic layer control by usingsequential release of gas phase precursors. The deposition can compriserepeated sequences of pulse-purge cycles of each precursor. The cyclecan start with exposure of a first precursor, followed by reaction andpurge (e.g., evacuation) of the reaction chamber to remove non-reactedand excess gases. Each reaction cycle can add a certain amount ofmaterial (e.g., growth-rate) on a surface. Growth rate can be controlledby cycle duration and precursor gas concentrations, temperature andsimultaneous exposure of the precursors. Self-limiting surface reactioncan help control of layer-by-layer deposition of a thin film, and lowdeposition temperature can make it compatible with back-end-of-lineprocessing. The phase change material can further be annealed fordensification.

In an aspect, successful deposition of GST thin films using ALD can beachieved for phase change memory. Precursor sets of Ge(N(CH₃)₂)₄,Sb(N(CH₃)₂)₄, Te(i-Pr)₂ and (Et₃Si)₂Te, SbCl₃, GeCl₂.C₄HgO₂ can be usedfor GeSbTe deposition. In an aspect, stoichiometric Ge₂Sb₂Te₅ can bedeposited by adjusting the exposure times and ratio of the binary cyclesGe—Te and Sb—Te.

The present methods and systems can be operational with numerous othergeneral purpose or special purpose computing system environments orconfigurations. Examples of well known computing systems, environments,and/or configurations that can be suitable for use with the systems andmethods comprise, but are not limited to, personal computers, servercomputers, laptop devices, and multiprocessor systems. Additionalexamples comprise set top boxes, programmable consumer electronics,network PCs, minicomputers, mainframe computers, distributed computingenvironments that comprise any of the above systems or devices, and thelike.

FIG. 16A is a block diagram illustrating an example reconfigurabledevice 1600. In an aspect, the reconfigurable device 1600 can beconfigured as a toggle device, a flip-flop device, a signal multiplexer,or a combination thereof. In an aspect, the reconfigurable device 1600can comprise a reconfigurable layer 1602. The reconfigurable layer 1602can comprise a phase change material. In an aspect, the reconfigurablelayer 1602 can be a structure, such as a three-dimensional structure.For example, the reconfigurable layer can comprise a cube structure,cylindrical structure, pyramidal structure. The reconfigurable layer1602 can be a substantially two-dimensional structure. For example, thereconfigurable layer 1602 can comprise a planar structure, a thin film,and/or the like. The phase change material can comprise a chalcogenidealloy.

In an aspect, the reconfigurable layer can comprise a closed surfacesurrounding, along at least one axis, a region at least partiallyenclosed by the reconfigurable layer. For example, the reconfigurablelayer can at least partially surround and/or enclose (e.g., along one ormore axis) a region. The region can comprise a cavity, an insulatinglayer, and/or the like. For example, the reconfigurable layer 1602 canbe formed as a tube (e.g., a pipe) or otherwise wrapped, distorted,twisted, and/or the like. The reconfigurable layer 1602 can comprise aclosed surface with an open top and/or open bottom. For example, thereconfigurable layer can comprise a four sided cube (e.g., partiallysurrounded the region). The cube can be hollow. The four sided cube canbe with a top or bottom. The reconfigurable layer can comprise apyramidal structure (e.g., without a top or bottom). It should be notedthat though the reconfigurable layer 1602 is shown with a left side anda right side, in some scenarios, the left side and right side can beseamlessly connected to form a three-dimensional structure (e.g., asshown in FIG. 3).

The reconfigurable device 1600 can comprise a set of contacts (e.g.,terminals, electrodes). The set of contacts can comprise at least afirst contact 1604, a second contact 1606, and a third contact 1608. Theset of contacts can comprise a fourth contact 1610, fifth contact 1612,sixth contact 1614, seventh contact 1616, eighth contact 1618, and/orthe like. The one or more contacts can be conductive. The one or morecontacts can be composed of a conductive material, such as TitaniumNitride (TiN) or other metal.

In an aspect, the set of contacts can be electrically connected (e.g.,coupled) and/or otherwise attached (e.g., connected) to thereconfigurable layer 1602. For example, an edge of one or more (or each)of the contacts of the set of contacts can be in contact with a firstside 1620 of the reconfigurable layer 1602. In an aspect, the set ofcontacts can comprise at least a first contact, a second contact, and athird contact. The first contact 1604 can be an input contact, an outputcontact, and/or a control contact (e.g., contact configured to write anderase amorphous regions). The second contact 1606 can be an inputcontact, an output contact, and/or a control contact. The third contact1608 can be an input contact, an output contact, and/or a controlcontact. For example, input contacts can provide signals (e.g.,currents) into the reconfigurable layer 1602. Output contacts canreceive signals (e.g., currents) from the reconfigurable layer 1602.Control contacts can be configured to modify the reconfigurable layer1602 by providing write and reset commands, signals, and/or the like tothe reconfigurable layer 1602. Control contacts can form amorphousregions, such as the first amorphous region 1624. Control contacts canalso cause amorphous regions to change to a crystalline form and/orliquid form.

In an aspect, the first contact 1604 can be positioned directly acrossor diagonally across the reconfigurable layer 1602 from the secondcontact 1606. The first contact 1604 and the third contact 1608 can belocated on a first side 1620 (e.g. top) of the reconfigurable layer1602. The second contact 1606 can be located on a second side 1622(e.g., bottom) of the reconfigurable layer 1602. The first side 1620 canbe opposite from the second side 1622. For example, the first side 1620can comprise a top of the tube. The second side 1622 can comprise abottom of the tube.

The reconfigurable device 1600 can comprise at least one control element1626 electrically coupled to one or more of the set of contacts. Itshould be noted, that though only two control elements 1626 are shown,it is contemplated that each contact of the set of contacts can beelectrically connected to a control element as illustrated elsewhereherein. Furthermore, multiple contacts can be connected to a singlecontrol element as illustrated elsewhere herein. For example, the atleast one control element 1626 can comprise one or more transistorsconfigured to supply signals (e.g., current, voltage) to one or more ofthe contacts. The at least one control element 1626 can be configured tosupply the first control signal to one or more of the set of contacts.The first control signal can be configured to modify a first portion ofthe reconfigurable layer 1602 thereby isolating the first contact 1604from the second contact 1606 and/or the third contact 1608. For example,the first control signal can be configured to isolate the first contact1604 from the second contact 1606 by forming a region of amorphous phasechange material within the reconfigurable layer 1602.

In another aspect, PMOS and NMOS can be utilized to isolate controloperation and toggle as described herein. For example, the at least onecontrol element 1626 can comprise a plurality of transistors. Forexample, the control contacts can be connected to a single transistor(e.g., NMOS), while the input contacts and the output contacts can beconnected to four corresponding transistors (e.g., PMOS). In an aspect,PMOS and NMOS can be interchanged.

In some scenarios, the first control signal can be configured to form acrystalline path between two contacts, as shown in FIG. 8A. For example,the first amorphous region 1624 can be modified to contain a conductivepath (e.g., crystalline path). The conductive path can be at leastpartially encased in the first amorphous region. An outer layer of thefirst amorphous region 1624 can be configured to isolate the crystallinepath from other contacts, such as the first contact 1604, the secondcontact 1606, the third contact 1608, and/or the fourth contact 1610.

In an aspect, the set of contacts can comprise one or more controlcontacts. For example, the fifth contact 1612, sixth contact 1614,seventh contact 1616, eighth contact 1618 can be configured as controlcontacts. For example, the fifth contact 1612 can be configured a form afirst amorphous region 1624 in the reconfigurable layer 1602 along apathway between the fifth contact 1612 and the eighth contact 1618. Forexample, the first amorphous region 1624 can be formed along a line,path, or barrier from one contact to another contact. The firstamorphous region 1624 can isolate an input contact (e.g., first contact1604, third contact 1608) from one or more output contacts (e.g., secondcontact 1606, fourth contact 1610). The first amorphous region 1624 canisolate an output contact (e.g., second contact 1606, fourth contact1610) from one or more input contacts (e.g., first contact 1604, thirdcontact 1608).

It should be noted that any of contacts of the set of contacts can beconfigured as control contacts. The control contacts can be configuredas input and/or ouput contacts to send and receive signals, such as datasignals. The first amorphous region 1624 can extend between an inputcontact and an output contact (e.g., as shown in FIG. 12A, FIG. 12B, andFIG. 13). The first amorphous region 1624 can also extend between twocontrol contacts.

FIG. 16B is a block diagram illustrating the example reconfigurabledevice 1600 after an example reconfiguration. The at least one controlelement 1626 can be configured to switch the reconfigurable device 1600(e.g., and reconfigurable layer 1602) from a first state (e.g., shown inFIG. 16A) to a second state. For example, the at least one controlelement 1626 can be configured to supply a second control signal to oneor more of the set of contacts. The reconfigurable layer 1602 can bemodified by applying a second control signal to one or more of the setof contacts electrically connected to the reconfigurable layer 1602. Thesecond control signal can change which of the set of contacts areisolated or not isolated. For example, the second control signal can besupplied to the sixth contact 1614 and the seventh contact 1616. Thesecond control signal can be configured to isolate the third contact1608 from the second contact 1606.

In an aspect, the second control signal can be configured to modify thereconfigurable layer 1602 by forming a second amorphous region 1628. Thesecond amorphous region 1628 can be formed along a path, line, and/orthe like between two of the contacts of the set of contacts (e.g., sixthcontact 1614 and seventh contact 1616). The second control signal can beconfigured to remove at least a portion of the first amorphous region1624 formed in step 1702 (e.g., causing the first contact to no longerbe isolated from the second contact). For example, the second controlsignal can cause the first amorphous region 1624 to recrystallize.

It should be noted, that the at least one control element 1626 can beconfigured to switch the reconfigurable device 1600 to a plurality ofother states and configurations as described throughout the presentdisclosure. For example, a third control signal can be configured toisolate the fourth contact 1610 from one or more of the first contact1604 and the third contact 1608. Amorphous regions can be formed (e.g.,as path, barrier) between the fifth contact 1612 and the sixth contact1614, between the seventh contact 1616 and the eight contact, and/or thelike. Amorphous regions can be formed as a plug around, in front of, orotherwise blocking a single contact. Amorphous regions can also beformed between input contacts and output contacts (e.g., between thefirst contact 1604 and the second contact 1606, between the thirdcontact 1608 and the fourth contact 1610).

In an aspect, the reconfigurable device 1600 can be configured based onthermal runaway, cross talk (e.g., thermal cross talk), specializedgeometry, and/or the like. For example, the set of contacts can beconfigured to cause at least a first path in the medium and a secondpath in the medium. The first path can be between an output contact andan input contact, such as between the first contact 1604 and the secondcontact 1606. The first path can be between two control contacts. Thesecond path can be between an input contact and an output contact, suchas between the third contact 1608 and the fourth contact 1610. Thesecond path can be between two control contacts.

The at least one control element 1626 can be electrically coupled to theset of contacts. The at least one control element 1626 can be configuredto selectively couple and/or uncouple a source to the set of contacts.For example, the at least one control element 1626 can be configured toswitch between coupling the source to the set of contacts and uncouplingthe source from the set of contacts. The source can comprise anelectrical source (e.g., current voltage) and/or other source. A firstcoupling (e.g., a first time selectively coupling, or a first couplingevent) of the source to the set of contacts can cause the first path tobecome more conductive than the second path. A second coupling (e.g., asecond time selectively coupling) of the source to the set of contactscan cause the first path to become more conductive than the second path.For example, the second coupling can occur next in time after uncouplingthe first coupling.

In an aspect, coupling the at least one control element 1626 to the setof contacts can modify a state of the first path and/or second path.Uncoupling the at least one control element 1626 from the set ofcontacts can modify a state of the first path and/o second path. Forexample, uncoupling the first coupling (e.g., changing from coupling afirst time being uncoupled) of the source to the set of contacts canmodify the first path to become more resistive than the second path.Modifying the first path can comprise forming an amorphous region in thereconfigurable layer (e.g., medium) within the first path. For example,uncoupling the second coupling (e.g., changing from coupling a secondtime to being uncoupled) of the source to the set of contacts can modifythe second path to become more resistive than the second path. Modifyingthe second path can comprise forming an amorphous region in thereconfigurable layer (e.g., medium) within the second path. Coupling theat least one control element 1626 to the set of contacts can cause thesource to be channeled through the first path and/or second path.Channeling of the source through the first path during the firstcoupling (e.g., first coupling event) can liquefy a region within thefirst path and/or recrystallize an amorphous region with the secondpath. Channeling of the source through the second path during the secondcoupling (e.g., second coupling event) can liquefy a region (e.g., forma filament) within the first path and/or recrystallize an amorphousregion within the first path.

The reconfigurable device 1600 can be configured with a variety ofgeometries and contact placement. For example, the first path can belocated close enough to the second path such that channeling of thesource through the second path during a coupling event (e.g., secondcoupling event) modifies a state (e.g., conductivity, resistivity,throughput) of the first path. The second path can be located closeenough to the first path such that channeling of the source through thefirst path while the device 1600 is coupled (e.g., during a firstcoupling event) modifies a state (e.g., conductivity, resistivity,throughput) of the first path. A first distance between the first side1620 and the second side 1622 where the first path is located can beshorter than a second distance between the first side 1620 and thesecond side 1622 where the second path is located. For example, thefirst path can be shorter than the second path.

FIG. 17 is a flowchart illustrating an example method for controlling asignal. At step 1702, a first state can be formed in a reconfigurablelayer. For example, the first state can be formed by applying a firstcontrol signal (e.g., one or more signals) to one or more of a set ofcontacts (e.g., terminals, electrodes). In an aspect, the first controlsignal can modify a first portion of the reconfigurable layer therebyisolating the first contact from the second contact, the third contact,and/or other contacts. The first control signal can be configured toisolate the first contact from the second contact by forming a firstamorphous region (e.g., region of amorphous phase change material)within the reconfigurable layer. For example, the first amorphous regioncan be formed as a path, line, barrier, and/or the like between at leasttwo of the contacts of the set of contacts. The first amorphous regioncan comprise a plug, bulge, and/or the like formed at (e.g., around,extending from) an end of a contact (e.g., as shown in FIG. 10).

In an aspect, the reconfigurable layer can be a structure, such as athree-dimensional structure. For example, the reconfigurable layer canbe formed as a tube (e.g., a pipe). The reconfigurable layer can be asubstantially two-dimensional structure. For example, the reconfigurablelayer can comprise a planar structure, a thin film, and/or the like. Thephase change material can comprise a chalcogenide alloy.

In an aspect, the set of contacts can be electrically connected (e.g.,coupled) and/or otherwise attached (e.g., connected) to thereconfigurable layer. For example, an edge of one or more (or each) ofthe contacts of the set of contacts can be in contact with an edge ofthe reconfigurable layer. In an aspect, the set of contacts can compriseat least a first contact, a second contact, and a third contact. As afurther example, the set of contacts can comprise 4 contacts, 6contacts, 7 contacts, 8 contacts, and/or other number as illustratedthroughout the present disclosure. The first contact can be an inputcontact, an output contact, and/or a control contact (e.g., contactconfigured to write and erase amorphous regions). The second contact canbe an input contact, an output contact, and/or a control contact. Thethird contact can be an input contact, an output contact, and/or acontrol contact.

In an aspect, the first contact (e.g., I₁, I₂) can be positioneddirectly across or diagonally across the reconfigurable layer from thesecond contact (e.g., O₁, O₂). The first contact and the third contact(e.g., I₁, I₂) can be located on a first side (e.g. top) of thereconfigurable layer. The second contact can be located on a second side(e.g., bottom) of the reconfigurable layer. The first side can beopposite from the second side. For example, the first side can comprisea top of the tube. The second side can comprise a bottom of the tube.

In an aspect, the set of contacts can comprise a first control contact(e.g., W₁, W₂) and a second control contact (e.g., W₃, W₄). For example,the first control signal can be configured a form the first amorphousregion in the reconfigurable layer along a pathway between the firstcontrol contact and the second control contact. For example, the firstamorphous region can be formed along a line, path, or barrier from theone contact to another contact. The region can isolate an input contact(e.g., first contact, third contact) from one or more output contacts.The first amorphous region can isolate an output contact (e.g., secondcontact, fourth contact) from one or more input contacts. The firstamorphous region can extend between an input contact and an outputcontact (e.g., as shown in FIG. 12A, FIG. 12B, and FIG. 13).

In an aspect, the set of contacts can comprise a fourth contact. Thefirst control signal can be configured to form a crystalline pathbetween the first contact and the fourth contact. The crystalline pathcan be at least partially encased in an amorphous region (e.g., firstamorphous region) configured to isolate the crystalline path from thesecond contact and the third contact.

At step 1704, a first output (e.g., first data output) can be receivedfrom the reconfigurable layer based on the first state of thereconfigurable layer. For example, a first signal can be provided to oneor more of the set of contacts. The signal can be transmitted across thereconfigurable layer based on the first state. For example, the firststate can select, divert, isolate, block, and/or the like one or moreoutputs (e.g., second contact, fourth contact) from receiving the firstsignal.

At step 1706, the reconfigurable layer can be switched (e.g., modified)to a second state. For example, the reconfigurable layer can be modifiedby applying a second control signal (e.g., one or more signals) to oneor more of the set of contacts electrically connected to thereconfigurable layer. The second control signal can change which of theset of contacts are isolated or not isolated. For example, the secondcontrol signal can be configured to isolate the third contact from thesecond contact. As another example, the second control signal can beconfigured to isolate the fourth contact from one or more of the firstcontact and the third contact. The fourth contact can be located on thesecond side of the reconfigurable layer.

In an aspect, the second control signal can be configured to form asecond amorphous region. The second amorphous region can be formed alonga path, line, and/or the like between two of the contacts of the set ofcontacts (e.g., a third control contact, fourth control contact). Thesecond control signal can be configured to remove at least a portion ofthe first amorphous region formed in step 1702 (e.g., causing the firstcontact to no longer be isolated from the second contact). For example,the second control signal can cause the first amorphous region torecrystallize.

At step 1708, a second data output can be received from thereconfigurable layer based on the second state. For example, a secondsignal (e.g., which may be the same as the first signal) can be providedto one or more of the set of contacts. The second signal can betransmitted across the reconfigurable layer based on the second state.For example, the second state can select, divert, isolate, block, and/orthe like one or more outputs (e.g., second contact, fourth contact) fromreceiving the second signal.

FIG. 18 is a flowchart illustrating an example method for reconfiguringa device. At step 1802, a first portion of a phase change structurebetween a first contact and a second contact can be melted. The firstcontact (e.g., terminal, electrode) can be connected (e.g., attached,electrically coupled) to the phase change structure. The first contact(e.g., terminal, electrode) can be connected (e.g., attached,electrically coupled) to the phase change structure. For example,melting the first portion can comprise applying a first voltage betweenthe first contact and the second contact,

At step 1804, an amorphous region can be formed around the firstportion. For example, a second voltage can be applied between the firstcontact and second contact. As another example, forming the amorphousregion can comprise reducing the first voltage to a second voltage. Thesecond voltage can be smaller than the first voltage. As anillustration, the first voltage can be approximately 1V, and the secondbe approximately 0.2 V. In an aspect, a filament (e.g., liquid portion)can be retained within the amorphous region (e.g., until latercrystallization).

At step 1806, the first portion can be crystallized thereby forming aconductive path from the first contact to the second contact.Crystallizing the first portion can comprise forming the conductive pathvia nucleation and growth. For example, growth can occur based on asolid (e.g., amorphous, crystalline) portion proximate the firstportion. In an aspect, the conductive path can be isolated, by theamorphous region, from a third contact connected to the phase changestructure.

At step 1808, a first signal can be provided through the conductivepath. For example, the first signal can comprise a data signal. Thefirst signal can be channeled to the second contact based on the firstsignal. In an aspect, a second signal can be provided through the phasechange structure between the third contact and a fourth contactconnected to the phase change structure.

FIG. 19 is a flow chart illustrating an example method for using a phasechange device. At step 1902, high-voltage, short-duration pulses can beapplied between a first set of contacts and a second set of contacts. Asan illustration, a voltage on the order of 1 Volt (e.g., 1, 2, 3 V orother voltage) can be applied for a time the order of 100 picoseconds(e.g., 100, 200 ps). The phase change material can be applied betweenthe first set of contacts and the second set of contacts. The phasechange material can be crystalline or amorphous. At step 1904, one ormore non-conducting paths can be formed between the first set ofcontacts and the second set of contacts via applying the high voltage,short duration pulses. At step 1906, long-duration (e.g., on the orderof a micro second), low-voltage pulses (e.g., on the order of 0.1 V) canbe applied between the first set of contacts and the second set ofcontacts. The low voltage pulses can be lower in voltage than the highvoltage pulses. The phase change material can be applied between thefirst set of contacts and the second set of contacts. For example, thephase change material can be amorphous. At step 1908, one or moreconducting paths can be formed between the first set of contacts and thesecond set of contacts via applying the long-duration, low-voltagepulse. As an example, the phase change material can be a chalcogenidealloy. In an aspect, a plurality of transistors can be electricallycoupled to the first and second sets of contacts

FIG. 20 is a flowchart illustrating an example method. At step 2002, afirst control signal can be applied on a control contact (e.g.,terminal, electrode) of a reconfigurable device, such as a phase changedevice. In an aspect, the first signal can be a clock controlled signal.In an aspect, the disclosed reconfigurable phase change device cancomprise a two dimensional structure (e.g. a tube structure, a planarstructure). The two dimensional structure can comprise phase changematerial. A plurality of contacts can be attached to the two dimensionalstructure. The plurality of contacts can comprise one or more controlcontacts, two or more input contracts, one or more output contacts,and/or the like. A plurality of control signals can be applied on one ormore control contacts such that one input terminal is isolated from theone or more output contacts at a time. In an aspect, the reconfigurabledevice can comprise a three dimensional structure (e.g., a block) and aplurality of contacts attached to the three dimensional structure. Thethree dimensional structure can comprise phase change material. Theplurality of contacts can comprise one or more control contacts, two ormore input contacts, and one or more output contacts. A plurality ofcontrol signals can be applied on one or more control contacts such thatan input contact can be isolated from one or more output contacts at atime. The reconfigurable device can be configured as a toggle device, aflip-flop device, a signal multiplexer, a memory device, and/or thelike.

At step 2004, a first amorphized path can be formed between at least twoof plurality of contacts. The first amorphized path can be formed byrapidly cooling a molten volume. The first amorphous path can isolateone input (e.g., a first input) contacts from output contacts, and otherinput contacts can remain connected by the crystalline phase changematerial.

At step 2006, a second control signal can be applied on the controlcontact. In an aspect, the second control signal can be a clockcontrolled signal. By sending the second control pulse, a current canflow between intact control contacts as it has a more conductive currentpath. In an aspect, step 2006 can comprise crystallizing the firstamorphous path by utilization of thermal cross talk (e.g., heatgenerated from step 2006 can be close enough to the first amorphizedpath to crystallize the first amorphized path).

At step 2008, a second amorphized path can be formed between the atleast two of the plurality of contacts. At least one of the plurality ofcontacts associated with the second amorphized path can be differentfrom at least one of the plurality of contact associated with the firstamorphized path. The first amorphized path can recrystallize. The secondamorphous path can isolate another input (e.g., a second input) contactfrom output contacts. The process can be repeated every time a controlsignal is sent, leading to toggling the inputs.

In an aspect, the disclosed reconfigurable device can be configured forthermal runaway utilization for electrical current path selection. Forexample, two paths (e.g., loads), a first path and a second path, can beconnected to the same source point. Due to device geometry orfabrication variations the first path may lose resistance faster thanthe second path. As the resistance of the first path decays (e.g.,decreases), the first path can drag (e.g., channel) more current and canlose even more resistance falling in a positive feedback situation.Utilizing this positive feedback phenomenon to selectively flow currentbetween two parallel paths is an aspect of the present disclosure.

In an aspect, the disclosed reconfigurable device can be configured forthermal cross talk. Forming contacts (e.g., on the same edge of areconfigurable layer) close to each other such that the heat generateddue to the operation at one contact will affect the active region at theother contact can lead to phase transition. Thermal cross talk isusually addressed as a problem that affects electronic device operationthe reconfigurable device utilizing uses thermal cross talk to achievelogic operation.

In an aspect, the reconfigurable device can be formed in a geometry thatallows isolation between certain inputs and the output and utilizing thethermal cross talk. For example, the reconfigurable device can comprisea multi-contact patch in the form a trapezoid, square, a disk, and/orthe like

With a slight modification on the device geometry example reconfigurabledevices were found to achieve much broader functionality based on theway the reconfigurable device's terminals were connected, the number ofreconfigurable devices used, and/or the like.

In an aspect, an example reconfigurable device can be configured as ann=0 undeterministic device. For example, the reconfigurable device cancomprise one device with the two control terminals that may be shorted.The reconfigurable device can be configured as a Toggle Multiplexer andflip-flop.

FIG. 21A is a schematic showing an example reconfigurable device. Theamorphous paths and how the amorphous path toggle after sending the samecontrol pulse are shown. FIG. 21B illustrates the relationship betweenan input signal (A) and the output signal (Y). The same input can resultin toggling the output between X1 and X2. FIG. 21C illustrates analternative configuration of the reconfigurable device in which theamorphous paths are to be formed between two distinct contacts insteadof having a shared contact.

These device configurations (e.g., shapes) may result in anun-deterministic first time operation. Then the reconfigurable devicecan toggle (e.g., switch) between the two states. This randomness couldbe useful in security applications and random number generation.

In an aspect, an example reconfigurable device can be configured as ann=0 deterministic device. By adjusting the geometry of thereconfigurable device to have a trapezoid or a triangle, the inputconnected to closer to the longer edge (e.g., X1 in this case) will havethe highest priority and will always be chosen when the device isinitialized.

FIG. 22A illustrates an example reconfigurable device configured as adeterministic device variant. In the case shown in the FIG. 22A, outputX1 will always be connected to the output terminal after pulsing theinitial all crystalline state. FIG. 22B shows the relationship betweenthe input signal A and the output signal Y.

In the n=0 configuration, 50% reduction in the footprint can be obtainedover other devices with the added feature of non-volatility. FIG. 23illustrates the size comparison of a typical toggle multiplexer to areconfigurable device configured as a toggle multiplexer.

FIG. 24 illustrates another example reconfigurable device. The examplereconfigurable device can be configured as an n=1 device (e.g., onedevice with the two control terminals or paths that are not shorted).For example, the reconfigurable device can be compared to a CMOScounterpart (JK flip-flop). When the two control terminals of thereconfigurable device are controlled independently, the reconfigurabledevice can operate like a JK flip-flop. The conventional CMOSJK-flip-flop requires 18 transistors while the reconfigurable device(e.g., PCM-JK) in this case may utilize only 6 transistors which isabout 66% savings in footprint with the added feature of non-volatility.

In an aspect, an example reconfigurable device can be configured as ann≧2 device (e.g., sequential n bit state machine). Connecting more thanone reconfigurable device in series in a way that the reconfigurabledevices share common control signals can result in sequential statemachine operation with 2^(n) states. State machines have a wide space ofapplications and are usually achieved by flip-flops. The examplereconfigurable device achieves the state machine operation with lessnumber of transistors and smaller footprint. Plus, the state machinesobtained by the reconfigurable device are non-volatile which makes thereconfigurable devices well suited for low and extremely low poweroperations.

FIG. 25 illustrates another example reconfigurable device. For example,the reconfigurable device can be configured as an n=3 device, such as athree bit state machine achieved by connecting three reconfigurabledevices in series with each other. The input and output transistors canbe removed to avoid crowdedness and may be configured similar to what isshown in FIG. 25. One or more (or each, every) control transistor isconnected to two terminals in two reconfigurable devices. Transistor B,for instance, can be connected to the short terminal of device 1 and thelong terminal of device 2.

FIG. 26A through FIG. 26G illustrate device operation for an example n=3reconfigurable device. FIG. 26A illustrates an initial state (allcrystalline) of the reconfigurable device. FIG. 26B illustrates sendingone pulse to transistor B. The pulse can amorphize the shorter terminalof device 1. FIG. 26C illustrates sending another pulse to transistor B.The pulse can amorphize the longer terminal of device 2. Sending morepulses to the B transistor may not change anything after this state.FIG. 26D illustrates sending another pulse to transistor C. The shorterterminal device 2 can pass most of the current and get amorphized. Asthe shorter terminal of device 2 is phase transitioning, cross thermaltalk can heat the previously amorphized strip and crystallize it. FIG.26E illustrates sending a pulse to transistor A. The pulse can amorphizethe shorter terminal of device 3. FIG. 26F illustrates sending anotherpulse to transistor A. The pulse can amorphize the longer terminal ofdevice 1 and crystallize device 1's shorter terminal through thermalcross talk. FIG. 26G illustrates sending another pulse to the transistorA. The pulse will not change anything and the machine will stay at thesame state.

Based on the sequence at which the transistors are controlled, differentstates can be achieved. Every state can have a unique input and outputrelationship. For instance, for the state shown in FIG. 26E, the inputscan be connected to the left of the devices. For example, input 1 ofeach device can be connected to the output terminal of the device to theleft. Meanwhile, for the state shown in FIG. 26F, the output of device 1is connected to the input terminal of device 2, and the output terminalsof devices 2 and 3 are connected to input 1.

FIG. 27 illustrates an example reconfigurable device. Different statesand operation can be achieved using different ways of device connection.For example, instead of having every control transistor connected toonly two reconfigurable devices, a transistor can be connected to nreconfigurable devices. The reconfigurable devices may not be needed toform a ring (e.g., the last device connected to the first).

In an aspect, example operation principles for the reconfigurable deviceare described below. As mentioned earlier, the way that thereconfigurable devices are connected and operated the device geometrycan determine operation of the reconfigurable device. To explain thebasic operation principles; a simple reconfigurable device configurationis discussed (e.g., n=0). The device in FIG. 22 can be drawn with itselectrical connections as shown below.

FIG. 28 illustrates a schematic of an example reconfigurable device.When transistor A as activated, the current will have two significantpaths. FIG. 29 illustrates another schematic of an examplereconfigurable device. Due to the geometry the reconfigurable device,path 1 may have less resistance and attract more current that path 2.FIG. 30 illustrates another schematic of an example reconfigurabledevice. In this case R₁<R₂ due to the geometric length difference.Furthermore, the resistance of R1 and R2 can be a function oftemperature and decay exponentially as current flows in path 1 and path2 due to joule heating and thermal runaway.

FIG. 31A illustrates another schematic of an example reconfigurabledevice. FIG. 31B is a graph illustrating the relationship of resistanceand temperature of the device of FIG. 31A. When the switch is closed,more current can flow in R1 than in R2. This will result in heating R1(e.g., path 1) more than R2 (e.g., path 2). Consequently, R1 resistancemay drop even further and will attract even more current. This positivefeedback may result in short-circuiting the R2 (e.g., depending on theminimum value that R1 will reach). In the context of phase changematerials, there are about 2-4 orders of magnitude in resistancedifference between an amorphous or crystalline phase and the moltenliquid phase. Hence, very minimal current will flow in the other path(e.g., path 2).

When the switch is open again, the molten phase change material canrapid melt-quench resulting in a crystalline to amorphous phasetransition. The amorphous phase has 2-4 orders of magnitude higherresistance compared with crystalline case.

FIG. 32A illustrates another schematic of an example reconfigurabledevice. FIG. 32B is a graph illustrating the relationship of resistanceand temperature of the device of FIG. 32A. When the switch is closed forthe second time, R1 can have much higher resistance compared with R2,and the current will mainly flow in R2 and experience the positivefeedback phenomenon discussed earlier. FIG. 33A illustrates anotherschematic of an example reconfigurable device. FIG. 33B is a graphillustrating the relationship of resistance and temperature of thedevice of FIG. 33A. As R2 heats up due the joule heating, R1 canexperience heat. Depending on the amount of heat R1 experiences, R1 willstart phase transitioning from the highly resistive amorphous to theconductive crystalline phase of the initial state, in growth from meltprocess. The resistance of R1 will start decreasing. However, even if R1reached the crystalline state more current may be flowing in R2 as R2 isin the most conductive, liquid phase. FIG. 34A illustrates anotherschematic of an example reconfigurable device. FIG. 34B is a graphillustrating the relationship of resistance and temperature of thedevice of FIG. 34A. When the switch is open, R2 can rapid melt-quenchand transition in to the highly resistive amorphous phase. R1 cantransition back to the crystalline phase. FIG. 35A illustrates anotherschematic of an example reconfigurable device. FIG. 35B is a graphillustrating the relationship of resistance and temperature of thedevice of FIG. 35A.

Although the principles here are discussed with the context of thermalcrosstalk and thermal runaway, these concepts can be extended to deviceswith materials other than phase change materials that exhibit adifferent form of resistance change due to a ‘runway’ and other forms ofcrosstalk.

FIG. 36 is a flowchart illustrating an example method for operating areconfigurable device. At step 3602, a source can be coupled to a set ofcontacts configured to channel the source across a medium though a firstpath and a second path. Coupling the source can cause the first path tobecome more conductive than the second path. In an aspect, coupling thesource can cause the first path to substantially short-circuit thesecond path.

The first path can be located close enough to the second path such thatchanneling of the source through the second path after the recouplingmodifies the conductivity of the first path. Channeling of the sourcethrough the second path during the second coupling can recrystallize anamorphous region within the first path.

The medium can comprise a first edge and a second edge. A first distancebetween the first edge and the second edge where the first path islocated can be shorter than a second distance between the first edge andthe second edge where the second path is located. For example, the firstpath can be shorter than the second path.

At step 3604, the source can be uncoupled from the set of contacts.Uncoupling the first set of contacts can cause the first path to becomeless conductive than the second path. Uncoupling the source from the setof contacts can modify the first path to become more resistive than thesecond path. Modifying the first path can comprise forming an amorphousregion in the medium within the first path.

At step 3606, the source can be recoupled to the set of contacts.Recoupling the first set of contacts can cause the second path to becomemore conductive than the second path. The recoupling can occur next intime (e.g., before any other coupling and/or uncoupling events) afteruncoupling the first coupling.

FIG. 37 is a flowchart illustrating an example method for operating areconfigurable device. At step 3702, a first command signal can beprovided to a device. The first command signal can cause a first statein the device. For example, the device can comprise a reconfigurabledevice as described herein. The device can comprises a set of contactsconfigured to channel command signals through one or more of a firstpath and a second path. At least a portion of the first command signalcan be channeled through the first path thereby causing the second pathto become more conductive (e.g., via thermal cross talk). For example,the amorphous region in the second path can be crystallized by theportion of the first command signal channeled through the first path.

The device can comprise a medium. For example, the medium can comprise areconfigurable layer as described herein. The medium can comprises afirst edge and a second edge. A first distance between the first edgeand the second edge where the first path is located is shorter than asecond distance between the first edge and the second edge where thesecond path is located.

At step 3704, a first output signal can be received from the devicebased on the first state of the device. For example, a first inputsignal can be provided to the device. The device can channel, direct,supply, and/or the like the first input signal to an output contactbased on the first state. The first command signal can be received,channeled, supplied, and/or the like primarily through the first path.For example, the first path can substantially short-circuit the secondpath (e.g., while the first input signal is being provided).

At step 3706, a second command signal can be provided to the device tocause a second state in the device. The second command signal can bereceived after receiving the first output signal. The second commandsignal can cause a second state in the device. At least a portion of thesecond command signal can be channeled through the second path therebycausing the first path to become more conductive (e.g., via thermalcross talk). Providing the second command signal can modify the secondpath to become more resistive than the first path. Modifying the secondpath can comprise forming an amorphous region in the medium within thesecond path. Providing the second command signal to the device canrecrystallize an amorphous region within the first path.

At step 3708, a second output signal can be received based on the secondstate. For example, a second input signal can be provided to the device.The device can channel, direct, supply, and/or the like the second inputsignal to an output contact based on the second state. The secondcommand signal can be received, channeled, supplied, and/or the likeprimarily through the second path. For example, the second path cansubstantially short-circuit the first path (e.g., while the secondcommand signal is being provided). The device can be configured toswitch between the first state and the second state each time an inputsignal is provided to and/or received by the device.

The processing of the disclosed methods and systems can be performed bysoftware components. The disclosed systems and methods can be describedin the general context of computer-executable instructions, such asprogram modules, being executed by one or more computers or otherdevices. Generally, program modules comprise computer code, routines,programs, objects, components, data structures, etc. that performparticular tasks or implement particular abstract data types. Thedisclosed methods can also be practiced in grid-based and distributedcomputing environments where tasks are performed by remote processingdevices that are linked through a communications network. In adistributed computing environment, program modules can be located inboth local and remote computer storage media including memory storagedevices.

While the methods and systems have been described in connection withpreferred embodiments and specific examples, it is not intended that thescope be limited to the particular embodiments set forth, as theembodiments herein are intended in all respects to be illustrativerather than restrictive.

Unless otherwise expressly stated, it is in no way intended that anymethod set forth herein be construed as requiring that its steps beperformed in a specific order. Accordingly, where a method claim doesnot actually recite an order to be followed by its steps or it is nototherwise specifically stated in the claims or descriptions that thesteps are to be limited to a specific order, it is in no way intendedthat an order be inferred, in any respect. This holds for any possiblenon-express basis for interpretation, including: matters of logic withrespect to arrangement of steps or operational flow; plain meaningderived from grammatical organization or punctuation; the number or typeof embodiments described in the specification.

It will be apparent to those skilled in the art that variousmodifications and variations can be made without departing from thescope or spirit. Other embodiments will be apparent to those skilled inthe art from consideration of the specification and practice disclosedherein. It is intended that the specification and examples be consideredas exemplary only, with a true scope and spirit being indicated by thefollowing claims.

1. An apparatus, comprising: a reconfigurable layer comprising a phasechange material, wherein the reconfigurable layer comprises a closedsurface surrounding, along at least one axis, a region at leastpartially enclosed by the reconfigurable layer; a set of contactsconnected with the reconfigurable layer, wherein the set of contactscomprises at least a first contact, a second contact, and a thirdcontact; and at least one control element electrically coupled with oneor more of the set of contacts, wherein the at least one control elementis configured to supply a first control signal to one or more of the setof contacts, and wherein the first control signal is configured tomodify a first portion of the reconfigurable layer thereby isolating thefirst contact from the second contact and the third contact.
 2. Theapparatus of claim 1, wherein the at least one control element isconfigured to supply a second control signal to one or more of the setof contacts, wherein the second control signal is configured to isolatethe third contact from the second contact.
 3. The apparatus of claim 1,wherein the first contact and the third contact are located on a firstside of the reconfigurable layer, and wherein the second contact islocated on a second side of the reconfigurable layer, and wherein thefirst side is opposite from the second side.
 4. The apparatus of claim1, wherein the first contact is positioned diagonally across thereconfigurable layer from the second contact.
 5. The apparatus of claim1, wherein the first control signal is configured to isolate the firstcontact from the second contact at least in part by forming a region ofamorphous phase change material within the reconfigurable layer.
 6. Theapparatus of claim 1, wherein the reconfigurable layer comprises a tube.7. The apparatus of claim 1, wherein the set of contacts comprise afirst control contact and a second control contact, and wherein thefirst control signal is configured to form an amorphous region in thephase change material along a pathway between the first control contactand the second control contact.
 8. The apparatus of claim 1, wherein theset of contacts comprise a fourth contact, and wherein the first controlsignal is configured to form a crystalline path between the firstcontact and the fourth contact, and wherein the crystalline path isencased in an amorphous region isolating the crystalline path from thesecond contact and the third contact. 9-20. (canceled)
 21. An apparatuscomprising: a medium; a set of contacts connected with the medium,wherein the set of contacts is configured to cause at least a first pathin the medium and a second path in the medium; and a control elementelectrically coupled with the set of contacts and configured toselectively couple a source to the set of contacts, wherein a firstcoupling of the source to the set of contacts causes the first path tobecome more conductive than the second path, and wherein a secondcoupling of the source with the set of contacts causes the first path tobecome more conductive than the second path.
 22. The apparatus of claim21, wherein uncoupling the first coupling of the source with the set ofcontacts modifies the first path to become more resistive than thesecond path.
 23. The apparatus of claim 22, wherein modifying the firstpath comprises forming an amorphous region in the medium within thefirst path.
 24. The apparatus of claim 21, wherein the first path isdisposed with respect to the second path such that channeling of thesource through the second path during the second coupling modifies aconductivity of the first path.
 25. The apparatus of claim 24, whereinchanneling of the source through the second path during the secondcoupling recrystallizes an amorphous region within the first path. 26.The apparatus of claim 21, wherein the second coupling occurs next intime after uncoupling the first coupling.
 27. The apparatus of claim 21,wherein the medium comprises a first edge and a second edge, and whereina first distance between the first edge and the second edge where thefirst path is located is shorter than a second distance between thefirst edge and the second edge where the second path is located.
 28. Amethod comprising: coupling a source to a set of contacts configured tochannel the source across a medium though a first path and a secondpath, wherein coupling the source causes the first path to become moreconductive than the second path; uncoupling the source from the set ofcontacts, wherein uncoupling the source from the set of contacts causesthe first path to become less conductive than the second path; andrecoupling the source to the set of contacts, wherein recoupling thesource to the set of contacts causes the first path to become moreconductive than the second path.
 29. The method of claim 28, whereincoupling the source to the set of contacts causes the first path tosubstantially short-circuit the second path.
 30. The method of claim 28,wherein uncoupling the source from the set of contacts modifies thefirst path to become more resistive than the second path.
 31. (canceled)32. The method of claim 28, wherein the first path is disposed withrespect to the second path such that channeling of the source throughthe second path after the recoupling modifies a conductivity of thefirst path.
 33. (canceled)
 34. The method of claim 28, wherein therecoupling occurs next in time after uncoupling the first coupling. 35.The method of claim 28, wherein the medium comprises a first edge and asecond edge, and wherein a first distance between the first edge and thesecond edge where the first path is located is shorter than a seconddistance between the first edge and the second edge where the secondpath is located. 36-43. (canceled)